当POP，push，dismiss，pressent连续调用的时候，要延迟会使用，
- (IBAction)goShoppingCartButtonAction:(id)sender
{
[self.navigationController popToRootViewControllerAnimated:NO];
[self performSelector:@selector(selectThirdTab) withObject:nil afterDelay:.3f];
}
- (void)selectThirdTab
{
MSAppDelegate *appDelegate = (MSAppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate.tabBarController setSelectedIndex:3];
}